The human immunodeficiency virus (HIV) and Acquired Immunodeficiency Syndrome (AIDS) epidemic has emerged as a major threat to public health. More than 250,000 persons have been diagnosed with AIDS and an estimated 1.5 million persons are infected with HIV in the U.S. Although originally an infection of gay white males in this country, increasingly HIV is infecting women, minority racial and ethnic populations, injecting drug users, and heterosexuals. An intensive basic and applied research effort has led to the clinical development of new HIV therapies at an accelerated pace. As new therapies come into use, data regarding appropriateness and effectiveness in the heterogeneous populations of patients for whom they are intended is often incomplete. A number of antiretroviral, antimicrobial, and ancillary therapies are currently available for managing HIV infection, and evidence suggests that the natural history of HIV disease has changed with the use of these drugs. To better assess the effectiveness and appropriateness of pharmaceutical therapies used in treating HIV disease, we propose to develop a comprehensive longitudinal database of individuals infected with HIV who are cared for in an urban primary setting. These data will be used to examine the effectiveness of antiretroviral and antimicrobial therapies in preventing progression of HIV disease and its opportunistic complications; to determine the association of surrogate laboratory markers with clinical outcomes; to delineate the frequency and consistency of prescription drug use and to identify sociodemographic and clinical characteristics of individuals with HIV associated with consistent use of, and response to, drug therapy. This database should serve as an important and rich resource to evaluate the evolving natural history of HIV infection treated with current and new pharmaceutical therapies.